如何修改NSNotificationCenter addObsever方法的实现

如何修改NSNotificationCenter addObsever方法的实现,首先想到的是继承一个子类自己实现方法.但是项目进行了很久，以前的没有用这个子类，要兼容以前的肯定不能这样写，最后想到用cateory+runtime方法直接替换addObsever方法.就如这样:

+(void)load {

    [self switchMethod];

}

- (void)addAvoidDuplicationObserver:(id)observer selector:(SEL)aSelector name:(NSString *)aName object:(id)anObject {//避免重复添加通知

    [self removeObserver:observer name:aName object:anObject];

    [self addAvoidDuplicationObserver:observer selector:aSelector name:aName object:anObject];

}

+ (void)switchMethod

{

    SEL addSel = @selector(addObserver:selector:name:object:);

    SEL myAddSel = @selector(addAvoidDuplicationObserver:selector:name:object:);

    

    Method systemRemoveMethod = class_getInstanceMethod([self class],addSel);

    Method DasenRemoveMethod = class_getInstanceMethod([self class], myAddSel);

    

    method_exchangeImplementations(systemRemoveMethod, DasenRemoveMethod);

}

git地址:无